第三章:基于BTrace的监控调试

本文主要参考慕课网若鱼老师课程Java生产环境下性能监控与调优详解

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本章关键词:BTrace、拦截、注意事项

一、入门

1.做什么的?

  • 可以在应用程序不重启,不修改的情况下,正在运行的情况下,动态的修改字节码,达到监控调试的目的
  • 可以动态的向目标应用程序的字节码注入追踪代码
  • 用到的技术

JavaComplierApi、JVMTI、Agent、Instrumentation+ASM

2.安装

  • 到官网中下载相应版本
  • 新建环境变量BTRACE_HOME,添加Path:%BTRACE_HOME%\bin

环境变量的添加请自行百度

  • 两种运行脚本方式
  1. JVisualVM中添加Btrace插件(参见上一章),添加classpath

2.使用命令行btrace

3.使用详解

  • 代码示例
    btrace需要引入三个jar,就是下载的btrace程序中,build目录下的三个


    jar包.png

引入jar包


        
            com.sun.btrace
            btrace-boot
            1.3.11
            jar
            system
            D:\btrace-bin-1.3.11\build\btrace-boot.jar
        

        
            com.sun.btrace
            btrace-agent
            1.3.11
            jar
            system
            D:\btrace-bin-1.3.11\build\btrace-agent.jar
        
        
            com.sun.btrace
            btrace-client
            1.3.11
            jar
            system
            D:\btrace-bin-1.3.11\build\btrace-client.jar
        

将要被拦截的代码

package com.qinxianyun.monitor_tuning.chapter4;

import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestParam;
import org.springframework.web.bind.annotation.RestController;

/**
 * @author Qinxianyun
 * @version V1.0
 * @time 2018/7/21.12:50
 * @description 演示btrace
 */
@RestController
@RequestMapping("ch4")
public class Ch4Controller {
    @RequestMapping("/arg1")
    public String arg1(@RequestParam("name")String name){
        return "hello," + name;
    }
}

btrace脚本(脚本和代码没有必要关联性,脚本可以随便写在哪里,没有必要写在方法的一个项目里面)

package com.qinxianyun.monitor_tuning.chapter4;

import com.sun.btrace.AnyType;
import com.sun.btrace.BTraceUtils;
import com.sun.btrace.annotations.*;

@BTrace
public class PrintArgSimple {
   
    @OnMethod(
            clazz = "com.qinxianyun.monitor_tuning.chapter4.Ch4Controller",
            method = "arg1",
            location = @Location(Kind.ENTRY)
    )
    public static void anyRead(@ProbeClassName String pcn, @ProbeMethodName String pmn, AnyType[] args){
        BTraceUtils.printArray(args);
        BTraceUtils.println(pcn + "," + pmn);
        BTraceUtils.println();
    }
}

@OnMethod表示我们要拦截哪个类的哪个方法,在什么时候进行拦截
Kind.ENTRY表示在入口的时候拦截(也就是一进入方法的时候)
@param pcn 拦截方法类的类名
@param pmn 拦截方法的方法名
@param args 参数

  • 进入到btrace脚本的目录下


    进入目录.png
  • 查看进程id


    查看进程id.png
  • 运行脚本文件


    运行中.png
  • 浏览器中输入http://localhost:8080/ch4/arg1?name=qinxianyun
    出现如下处理结果

    处理结果.png

  • Java VisualVM打开btrace(需要已经安装了插件,详情见上一章)


    vm打开btrace.png

    界面详解.png

    输出.png

二、拦截构造函数、同名函数

1.拦截方法(普通方法、构造方法、同名方法)

  • 普通方法 @OnMethod(clazz=" ",method=" ")

参考上面的例子

  • 构造函数@OnMethod(clazz=" ",method="")

因为构造函数在字节码层面是叫init,所以用

@RequestMapping("/constructor")
    public User arg1(User user){
        return user;
    }
package com.qinxianyun.monitor_tuning.chapter2;

/**
 * @author Qinxianyun
 * @version V1.0
 * @time 2018/7/15.14:52
 * @description 用户实体
 */
public class User {
    private int id;

    private String name;

    public User(int id, String name) {
        this.id = id;
        this.name = name;
    }

    public int getId() {
        return id;
    }

    public void setId(int id) {
        this.id = id;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }
}

package com.qinxianyun.monitor_tuning.chapter4;

import com.sun.btrace.AnyType;
import com.sun.btrace.BTraceUtils;
import com.sun.btrace.annotations.BTrace;
import com.sun.btrace.annotations.OnMethod;
import com.sun.btrace.annotations.ProbeClassName;
import com.sun.btrace.annotations.ProbeMethodName;

@BTrace
public class PrintConstructor {

    @OnMethod(
            clazz = "com.qinxianyun.monitor_tuning.chapter2.User",
            method = ""
    )
    public static void anyRead(@ProbeClassName String pcn, @ProbeMethodName String pmn, AnyType[] args){
        BTraceUtils.println(pcn + "," + pmn);
        BTraceUtils.printArray(args);
        BTraceUtils.println();
    }
}
运行结果.png
  • 同名方法(用参数区分)
@RequestMapping("/same1")
    public String same(@RequestParam("name")String name){
        return "hello," + name;
    }

    @RequestMapping("/same2")
    public String same(@RequestParam("name")String name,@RequestParam("id")int id){
        return "hello," + name + "," +id;
    }
package com.qinxianyun.monitor_tuning.chapter4;

import com.sun.btrace.AnyType;
import com.sun.btrace.BTraceUtils;
import com.sun.btrace.annotations.BTrace;
import com.sun.btrace.annotations.OnMethod;
import com.sun.btrace.annotations.ProbeClassName;
import com.sun.btrace.annotations.ProbeMethodName;

@BTrace
public class PrintSame {
    @OnMethod(
            clazz = "com.qinxianyun.monitor_tuning.chapter4.Ch4Controller",
            method = "same"
    )
    public static void anyRead(@ProbeClassName String pcn, @ProbeMethodName String pmn, String name ,int id){
        BTraceUtils.println(pcn + "," + pmn + "," + name + "," + id);
        BTraceUtils.println();
    }
}

拦截重载的方法,是根据参数的类型区分的,脚本中的名字可以和代码中参数名不一致

运行结果:


运行结果1.png

三、拦截返回值、异常行号

1.拦截时机

  • Kind.ENTRY : 入口,默认值

参考第一个例子

  • Kind.RETURN : 返回
package com.qinxianyun.monitor_tuning.chapter4;

import com.sun.btrace.AnyType;
import com.sun.btrace.BTraceUtils;
import com.sun.btrace.annotations.*;

@BTrace
public class PrintReturn {
    @OnMethod(
            clazz = "com.qinxianyun.monitor_tuning.chapter4.Ch4Controller",
            method = "arg1",
            location = @Location(Kind.RETURN)
    )
    public static void anyRead(@ProbeClassName String pcn, @ProbeMethodName String pmn, @Return AnyType result){
        BTraceUtils.println(pcn + "," + pmn + "," + result);
        BTraceUtils.println();
    }
}

  • Kind.THROW : 异常
package com.qinxianyun.monitor_tuning.chapter4;

import com.sun.btrace.BTraceUtils;
import com.sun.btrace.annotations.*;

@BTrace
public class PrintOnThrow {
    @TLS
    static Throwable currentException;

    @OnMethod(
            clazz = "java.lang.Throwable",
            method = ""
    )
    public static void onthrow(@Self Throwable self){//new Throwable()
        currentException = self;
    }

    @OnMethod(
            clazz = "java.lang.Throwable",
            method = ""
    )
    public static void onthrow1(@Self Throwable self,String s){//new Throwable(String msg)
        currentException = self;
    }

    @OnMethod(
            clazz = "java.lang.Throwable",
            method = ""
    )
    public static void onthrow1(@Self Throwable self,String s,Throwable cause){//new Throwable(String msg,Throwable cause)
        currentException = self;
    }

    @OnMethod(
            clazz = "java.lang.Throwable",
            method = ""
    )
    public static void onthrow2(@Self Throwable self,Throwable cause){//new Throwable(Throwable cause)
        currentException = self;
    }

    @OnMethod(
            clazz = "java.lang.Throwable",
            method = "",
            location = @Location(Kind.RETURN)
    )
    public static void onthrowreturn(){
        if (currentException != null){
            BTraceUtils.Threads.jstack(currentException);
            BTraceUtils.println("========================");
            currentException = null;
        }
    }
}

  • Kind.Line :行
package com.qinxianyun.monitor_tuning.chapter4;

import com.sun.btrace.BTraceUtils;
import com.sun.btrace.annotations.*;

@BTrace
public class PrintLine {
    @OnMethod(
            clazz = "com.qinxianyun.monitor_tuning.chapter4.Ch4Controller",
            location = @Location(value = Kind.LINE,line = 41)
    )
    public static void anyRead(@ProbeClassName String pcn,@ProbeMethodName String pmn,int line){
        BTraceUtils.println(pcn + "," + pmn + "," + line);
        BTraceUtils.println();
    }
}

四、拦截复杂参数、环境变量、正则匹配拦截

1.拦截this、入参、返回

  • this:@Self
  • 入参:可以用AnyType,也可以用真实类型,同名的用真实的
  • 返回:@Return

2.获取对象的值

  • 简单类型:直接获取
  • 复杂类型:反射,类名+属性名
package com.qinxianyun.monitor_tuning.chapter4;

import com.qinxianyun.monitor_tuning.chapter2.User;
import com.sun.btrace.BTraceUtils;
import com.sun.btrace.annotations.*;

import java.lang.reflect.Field;

@BTrace
public class PrintArgComplex {
    @OnMethod(
            clazz = "com.qinxianyun.monitor_tuning.chapter4.Ch4Controller",
            method = "arg2",
            location = @Location(Kind.ENTRY)
    )
    public static void anyRead(@ProbeClassName String pcn, @ProbeMethodName String pmn, User user){
        BTraceUtils.printFields(user);
        Field field2 = BTraceUtils.field("com.qinxianyun.monitor_tuning.chapter2.User","name");
        BTraceUtils.println(BTraceUtils.get(field2,user));
        BTraceUtils.println(pcn + "," + pmn);
        BTraceUtils.println();
    }
}

注意:
复杂类型.png

引用的需要加上-cp

3.正则表达式

  • 拦截任意方法
package com.qinxianyun.monitor_tuning.chapter4;

import com.sun.btrace.BTraceUtils;
import com.sun.btrace.annotations.*;

@BTrace
public class PrintRegex {
    @OnMethod(
            clazz = "com.qinxianyun.monitor_tuning.chapter4.Ch4Controller",
            method = "/.*/"
    )
    public static void anyRead(@ProbeClassName String pcn, @ProbeMethodName String pmn){
        BTraceUtils.println(pcn + "," + pmn);
        BTraceUtils.println();
    }
}

4.打印环境变量

  • 打印(输出类似Jinfo命令)
package com.qinxianyun.monitor_tuning.chapter4;

import com.sun.btrace.BTraceUtils;
import com.sun.btrace.annotations.BTrace;

@BTrace
public class PrintJinfo {
    static {
        BTraceUtils.println("System Properties:");
        BTraceUtils.printProperties();
        BTraceUtils.println("VM Flags:");
        BTraceUtils.printVmArguments();
        BTraceUtils.println("OS Enviroment:");
        BTraceUtils.printEnv();
        BTraceUtils.exit();
    }
}
  • 输出结果


    输出.png

注意事项:
1.默认只能本地运行
2.生产环境下可以使用,但是被修改的字节码不会被还原(即使btrace退出)
因此,脚本中不要有太耗系统资源的东西,否则会影响服务器。

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